The present invention relates generally to a high-tension line having a metallic housing section at ground potential, and more particularly relates to a high-tension line having a gas filling.
The present invention is an improvement on the state of the art of encased gas-insulated high-tension lines as described in the published German patent application No. 2 202 401. The casing of the high-tension line is formed in the known arrangement by an insulative material, into which material is imbedded a metallic screen either in a lattice construction or in the form of a foil. The metallic screen which is designed to contain the electric field against the outside, is galvanically connected to grounding bars which are located inside the casing and connected rigidly with the casing. The metallic grounding bars are dimensioned so that they will be able to carry any arising arc current for a longer period of time or to respectively conduct the current to a specific firing point where the arc can continue until the high-tension line is switched off.
The manufacture of an electric screen, embedded in the housing covering made of synthetic materials, is difficult and costly in view of the barrier field strength involved. The grounding bars, which are placed inside the casing, also necessitate an increase in the casing diameter.
Accordingly, it is a primary object of the present invention to provide an encased gas-insulated high-tension line (especially in regions of tension lines that are endangered by arc generation) with an economically produced jacket tube, thereby providing a protection against melting. Furthermore, it is another object to provide a jacket which can be applied in a simple manner and which can be manufactured at low costs.
Still another object is to provide a high-tension line which overcomes the problems of the prior art. The use of a metallic casing has the advantageous result that a gas filling, for example SF.sub.6 gas, will not come in contact with the insulative covering which is used as protection against melting. The insulative covering need not be free from inclusions, making it possible to utilize any proper, relatively inexpensive insulative material. It is also feasible to improve the arc protection of already existing installations, or to increase their short-circuit power if necessary, by a supplemental application of the insulative covering without the need for disassembly or shut-down of the system. The insulative covering will also provide the casing with a greater strength against cracking. The diameter of the casing can be held to an optimum size and is not influenced by any danger of local arc formation.